Rafael Nadal Withdraws From the ATP Finals With a Knee Injury

But the third set proved a step too far for Nadal, who won six titles this year. He began to struggle with his movement and was in visible pain. Goffin secured a double break to go ahead by 4-1, but Nadal rallied once more. He could retrieve only one of the breaks.

“It was tough even if he was not moving 100 percent,” Goffin said. “He was hitting the ball really hard. It’s never easy to finish a match, to finish a set against him. Even if I lost four match points in the second, I had no regret. I kept going in the third.”

Nadal ominously waved goodbye as he left the court, bringing to an end another auspicious season. He won his 10th French Open in June, added a third United States Open in September and, at 31, became the oldest man to end the year atop of the rankings.

With the Australian Open more than two months away, Nadal was confident playing in London would not have done any lasting damage. He said the injury was “nothing new.”

“Everybody of my team, we have the right experience on this thing,” he added. “We hope to manage it well, to have the right rest, the right work, and try to be ready for the beginning of the next season.”

Nadal’s exit simplifies Roger Federer’s path to a seventh ATP Finals title. The winner of the Australian Open and Wimbledon this year, Federer returns to action against Alexander Zverev on Tuesday after defeating Jack Sock on Sunday.

Grigor Dimitrov, making his ATP Finals debut, withstood a comeback attempt from Dominic Thiem and held on for a 6-3, 5-7, 7-5 victory on Monday.

The sixth-ranked Dimitrov maintained his focus despite being narrowly denied a chance to serve out the match in the second set, and then being broken at his first chance in the third.

“Every year you learn more about yourself, about the game, about the players,” Dimitrov said. “I’ve done also a lot of work on and off the court. It’s finally starting to kind of, like, come together.”